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Calibration methods and circuits to calibrate drive current and termination impedance

  • US 9,391,613 B2
  • Filed: 10/15/2015
  • Issued: 07/12/2016
  • Est. Priority Date: 09/08/2003
  • Status: Active Grant
First Claim
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1. An integrated circuit (IC) chip comprising:

  • transceiver circuits, each including a driver circuit to transmit data, a receiver circuit to receive data, each driver circuit including an on-die termination element exhibiting a termination impedance;

    a termination control circuit coupled to the transceiver circuits, the termination control circuit to calibrate the termination impedances and a voltage swing of the driver circuits, the termination control circuit including;

    a reference-impedance pad to couple to a reference resistor external to the chip;

    a reference-voltage pad to couple to a reference voltage source external to the chip;

    a comparator to compare a reference-resistor voltage on the reference-impedance pad with an external reference voltage on the reference-voltage pad and develop first control settings responsive to the comparison; and

    an adjustable impedance, coupled to the comparator, the comparator to compare the reference-resistor voltage on the reference-voltage pad with a voltage from the adjustable impedance to develop second control settings responsive to the comparison between the reference-resistor voltage and the voltage from the adjustable impedance; and

    a bus extending between the termination control circuit and the transceiver circuits, the bus to communicate the first control settings to the transceiver circuits.

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